A nebula is a cloud that roams through space and has no shape at all,and is made of helium,hydrogen,plasma and mostly dust like the one of the most famous nebula's called the hourse head nebula here's a picture to show you how it looks like so here http://www.nasa.gov/images/content/52238main_MM_image_feature_89_jw4.jpg
sometimes can make stellar evolution happen meaning a star canbe born by losing outer layer to make a red giant { A red giant star is a star that looks like are sun and is big like are sun} then when that happens it gains helium and hydrogen and a few other things when that is all is released it becomes a planatary nebula. like the one underneath these words the one down there is called the ring nebula. when the gas inside of a planatary nebula diffuse's it then becomes invisable and then becomes a white dwarf star.
Ring Nebula (M57)
the ring nebula
The ring nebula 2,300 light years away in the constellation of Lyra, and the star at the center of the Ring nebula has a surface temperature of 216,000 degrees Farenheit or 120,000 degrees celcius
http://www.nasa.gov/images/content/52238main_MM_image_feature_89_jw4.jpg
sometimes can make stellar evolution happen meaning a star canbe born by losing outer layer to make a red giant { A red giant star is a star that looks like are sun and is big like are sun} then when that happens it gains helium and hydrogen and a few other things when that is all is released it becomes a planatary nebula. like the one underneath these words the one down there is called the ring nebula. when the gas inside of a planatary nebula diffuse's it then becomes invisable and then becomes a white dwarf star.
http://www.daviddarling.info/encyclopedia/P/planneb.html
this video will tell you about the nebulas and how they are beautiful and awesome in every way
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